Hollow article manufacture by fluid pressure



Jan. 11, 1966 c. A. HEUER 3,228,223

HOLLOW ARTICLE MANUFACTURE BY FLUID PRESSURE Original Filed April 29, 1957 3 Sheets-Sheet 1 INVENTOR.

FIG -4 CHARLES A. HEUER Z/MZW A T TOR/V5 V Jan. 11, 1966 c. A. HEUER 3,228,223

HOLLOW ARTICLE MANUFACTURE BY FLUID PRESSURE Original Filed April 29, 1957 3 Sheets-Sheet 2 7 INVEN CHARLES A. HE R M? 14 ime A T TORNEV Jan. 11, 1966 c. A. HEUER 3,228,223

HOLLOW ARTICLE MANUFACTURE BY FLUID PRESSURE Original Filed April 29, 1957 3 Sheets-Sheet 5 Zw. 5106M A T TORNE V United States Patent Office 3,228,223 Patented Jan. 11, 1966 HGLLOW ARTICLE MANUFACTURE BY FLUID PRESSURE Charles A. Heller, East Alton, lll., assignor t Olin Mathieson Chemical Corporation, a corporation of Virginia Application Sept. 1, 1960, Ser. No. 54,565, now Patent No. 3,180,011, dated Apr. 27, 1965, which is a continuation of application Ser. No. 655,576, Apr. 29, 1957.

Divided and this application Nov. 13, 1964, Ser. No.

9 Claims. (Cl. 72-61) This invention relates to the fabrication from sheetlike material of hollow articles and more specifically to the manufacture of such articles having one face substantially smooth or flat and suitable for various uses such as the freezing unit of an ice maker. This application is a division of impending application Serial No. 54,565, filed September 1, 1960, now United States Patent 3,180,011, issued April 27, 1965, which in turn is a continuation of Serial No. 655,576, filed April 29, 1957, now abandoned.

The hollow sheet metal panels, although they may be made by various methods, are most advantageously and preferably made by a process such as described in U. S. Patent 2,690,002 issued September 28, 1954. This invention is particularly applicable to such a process wherein one of the weldable surfaces of one of a pair of component sheets is provided with a weld-preventing material in a definite pattern which over the area of the pattern will prevent welding of the areas separated by the weldpreventing material while in the areas not so separated the component sheets are unified in any suitable manner such as by hot rolling, after which welding operation the resultant blank is subjected to further manipulations for the purpose of expanding its unjoined portions by injection of inflation fluid under suitable pressure to permanently distend one side of the blank in the unjoine-d patterned area to develop the finished cavity or passageways of the hollow article.

An object of this invention is the fabrication of hollow articles in which the distention occurs on one side while the other side remains undistended and substantially smooth or fiat. Another object is to provide distentions of a certain desired external configuration on the side of the blank deformed by fluid pressure and more specifically to provide a flat topped passageway or cavity protrusion on the side opposite the undistended side. Still another object of the invention is to provide freedom from surface bending and sinking which is manifested as improved smoothness or flatness on the undistended side of the blank. A further object is to provide an improved inflation apparatus for the preparation of the finished article. A still further object is to provide novel apparatus for fabricating hollow panels inflated to form protrusions on one side only as described in the aforementioned US. Patent 2,690,002, so that the undistended surface has an exceptionally high degree of smoothness or flatness.

Other objects and advantages will be apparent from the following description of a specific embodiment illustrated in the drawing in which:

FIGURE 1 is a perspective view of one suitable blank from which a hollow panel containing conduit passageways is to be formed in accordance with this invention;

FIGURE 2 is a fragmentary perspective view partially in section taken on line 11-11 of FIGURE 1 showing part of the finished articles developed from the blank;

FIGURE 3 is a fragmentary perspective view showing general features of apparatus for practice of this invention;

FIGURE 4 is a fragmetary plan view showing the fluid pressure connections with respect to the surrounding part of the lower platen of the apparatus of FIGURE 3;

FIGURE 5 is an elevational View in cross section taken across the apparatus of FIGURE 3 after closure showing additional details of the apparatus and also the inflated article developed in the apparatus;

FIGURE 6 is a semi-schematic elevational view in cross section showing another form of suitable apparatus with another blank in position for inflation;

FIGURE 7 is a partial view of the apparatus of FIG- URE 6 at full inflation of the blank;

FIGURE 8 is a cross sectional view showing a modified form of apparatus for expansion of the bulbous parts of the finished article;

FIGURE 9 is a cross sectional view of part of another form of blank adapted for practice of this invention;

FIGURE 10 is a cross-sectional view of part of a rnodified form of blank found to be especially advantageous; and

FIGURE 11 is a cross sectional view of part of a still further modification of blank.

In accordance with this invention expansion of an inflatable blank is done while the blank is subjected to external confinement between at least one rigid die member and a body of fluid under pressure applied externally to only one side of the blank. One of the rigid die members, in the form of a press platen with a suitably shaped die surface, such as a flat one in particular, acts on one side of the blank while the fluid, and preferably a suitable incompressible liquid such as water, oil or the like, acts on the other side of the blank so a to constrain it between the die surface and the fluid or liquid during the continued application of inflation fluid pressure internally of the blank. The externally applied fluid pressure provides the confinement or constraint which Was found to result in improved hold-down action for the purpose of obtaining superior resistance to distention on one side of the blank while the other is distended.

External application of the hold-down fluid pressure has been found to give not only improved resistance to undesired bending and distortion in the side of the blank to remain undistended but to also provide improved expansion of the distended portions of the blank to final finished size and shape.

It is also contemplated that in accordance with this invention one-sided expansion will occur not only with the aid of external fluid pressure but also with the aid of a second rigid die member which acts together with the hold-down fluid to control the height and the shape of the expanded portions of the blank. Such member may also in addition act to prevent rupturing during expansion at higher pressure diiferentials between the internally and externally applied fluid pressures. The Working surface of the second member may be recedable from the first and continuously contact the distention during expansion. Such second rigid die member is ordinarily recessed to a depth corresponding to the final height of distention. during expansion. Such second rigid die member is ordinarily recessed to a depth corresponding to the final height of distention, but the depth may be varied by any suitable means such as shims retained in the bottom of the recess. It is contemplated that such shims be of the replaceable type retained by readily releasable means and specifically by magnetic means.

The periphery of the recess is sealed upon the blank to prevent access of the external pressure to the other side which is to remain undistended and to be pressed against the first rigid die member and take its shape, which may be that of a flat or gently curved plane. Between the blank and this first or usually flat die no deforming fluid pressure is to be applied; and to further avoid any change occurrence of it, whether by entrapment or otherwise,

suitable venting means may be employed-such as an interposed screen or such as venting ducts .or poresin the die member. Thus the die member may be constructed of porous metal for venting and may have a vacuum connection. Furthermore, for venting purposes either the face of this die member or the to-be-juxtaposed face of the blank could be provided with scoring or scratching where necessary for the best expansion. Where pressure relief is not provided in the apparatus, pressure relieving surfacing such as knurling, scratching or the like may be employed in the blank.

The periphery of the recess is preferably a surrounding ridge adapted to clamp and preferably indent the periphery of the blank to effect an excellent seal. The ridge may be sharp, rounded or flat. A sealing gasket of any suitable type, such as an element of deformable or resilient material, may also be used with or instead of the ridge.

Various pressure levels, both internal and external, and various, pressure level differentials are contemplated and may be varied in accordance with the type of blank employed, the thicknesses of the blank, the degree of distention desired and the shape and configuration of the distentions to be produced. In accordance with the concept of this invention, the operator need merely make the necessary variations and adjustments until the desired distentions are obtained on one side of the blank together with suitable freedom from distentions on the other side. The best results are obtained for each blank with the desired cavity configuration and height of distention at some particular combination of internal and external pressure to be determined in each instance by the operator.

The external or hold-down pressure may be applied simultaneously with the internal expansion pressure but is preferably applied ahead of it to minimize initial distortions which can be erased only with difliculty, if at all. Similarly, the pressures are preferably released simultaneously, which in some instances may be accomplished automatically by release of the internal pressure. While simultaneous release of the pressures is preferred it is permissible under certain conditions of operation to release the internal pressure prior to external pressure but in no event should the external pressure be released before the internal pressure unless or until the internal pressure is low enough after one-sided distention has been accomplished so as not to impart a further distention to the other side, which is to remain substantially unexpanded. In some cases premature release of internal pressure may cave in the crests, and particularly flattened crests, of the distended portion of the article.

Although various inflatable blanks are contemplated for working in accordance with this invention, it has been found that surface deforamtion and/or hardening of the blank on the side to remain uninflated imparts to it an improved tendency to remain flat on one side and adapts it especially for this invention. Such a surface condition may be obtained by scratching, knurling, embossing, indenting and the like. A most severe and uniform surface effect is obtained by shot peening.

A suitable form of blank 1 is shown in FIGURE 1 and includes a particular configuration of internally unjoined area 2 which extends to a peripheral parting line 3 at which internal pressure may be applied to expand the blank. After expansion the blank may be cut through another unjoined portion 4 to which another connection may be made.

Following expansion in accordance with this invention, one surface 5 of the blank 1 remains undistended as shown in FIGURES 1 and 2 while the other is distended at 8 to form the cavity or passageways 9 of the finished article 10 shown in FIGURE 2.

Forming of the finished article occurs in accordance with this invention in suitable apparatus, such as that shown in FIGURES 3, 4 and 5, characterized by an upper unrecessed die or platen 11 and a lower platen 13 having a suitable recess 14. Ridge 15 surrounds die recess 14 .as its rim and is adapted to press the blank 1 against the unrecessed or flat surface 12 of die member 11. Ridge 15 terminates at spaced peripheral portions 18 and 19 to make a suitable connection with the internal fluid pressure clamping members 22 and 23 adapted to coact with the fluid inlet means 16 which is placed to extend between the die members into blank opening 3 in any suitable manner and with the aid of clearance supplied by groove 20. Upon closure of the platens upon the blank, holddown fluid pressure is applied to one side of the blank through opening 25 of the recessed die member 13 through any suitable connection such as 17.

In FIGURE 5 the inflated blank making article 10 is shown with distentions 8 of final finished size expanded to a height determined by the presence of shims 28 and 29. These are retained with reliability in the bottom of the die recess 14 by means of a series of magnetic devices 27 which advantageously take the form of externally screw threaded studs of non-magnetic material such as bras-s or stainless steel having U-shaped permanent magnets contained therein with the pole faces at the tops of the studs 27 facing the shims. Lower die member 13 preferably contains a check valve for fluid pressure relief.

The pressure relief valve consists of a ball check 32 normally engaging a conical seat 33 to close discharge bore 37 from the inlet opening 25 unless the pressure fluid 140 exceeds a predetermined pressure level. The desired pressure level is maintained by means of a vented follower 35 and a coil spring 38 mounted in the bore 37 to act with adjustable compression on the ball 32.

Excessive pressure is bled off through vents 36 and the bore 37. Excessive pressure of the fluid 140 would manifest itself in springing of the die faces from each other to some positions such as 200 and 201 with-resultant undesired variation in the distended height of the expanded portions 8. Furthermore, sprung press platens would have the tendency, undesirable under certain conditions of operation, of acting as bellows so as to give the fluid the characteristics of a compressible fluid or a resilient medium.

Hydraulic fluid 140 is first applied in the recess through die conduit 31 and recess inlet 25 against the blank as it is pressed on rims 15 by means of the other die member 11. Fluid 140 is preferably a liquid such as water applied at a suitable pressure such as 1000 p.s.i. Next the inflation fluid is applied internally of the blank to accomplish expansion while the pressure of fluid 140, continued to be applied externally of the blank, maintains and reshapes the expanding blank in such a Way as to hold it flat against the unrecessed die member 11. Fluid 90, preferably a liquid such as water, is applied at a pressure suitably in excess of the pressure of liquid 140 to accomplish the result desired. An inflation pressure from about 2800-3000 p.s.i., for example, has been found suitable in combination with an external hold-down pressure of about 1000 p.s.i. to shape one certain thickness of a certain metal blank. It will be understood that other pressure levels and differentials may be employed as found necessary with the various hardnesses and thicknesses of the blanks used. In any event, the operator will vary the pressures and employ that differential of pressure found necessary in each particular instance to provide suitable freedom from distention on one side.

In the modification of FIGURES 6 and 7, a blank is placed between an upper flat platen 41 having a flat face 42 and a lower complementary recessed die 43 having the peripheral rim 45 and the sealing gasket 46 of any suitable resilient material, such as rubber. Lower die 43 is also provided with a suitable number of screw-controlled advancing and retreating members 47 for controlling the volume of liquid 141 in the die recess. Control is obtained by the screw down 50 connected in any suitable manner such as by gear 49 to mating gears 48 on the members 47. These members limit the sag of the blank 100 upon its being placed between the open platens as shown in FIGURE 6 to rest on the peripheral gasket 46. The amount of sag of the blank 100 and the displacement of the members 47 in the die recess determine the volume of liquid displaced from the die recess and the working volume 141 remaining therein. The apparatus also includes suitable venting means such as the screen 52 between the blank 100 and the platen 41.

In operation, closure of the apparatus compresses the gasket 46 to seal the liquid 141 in the cavity and also compresses the blank 100 against the rim 45 which in this particular modification has a height equal to the desired distance of the to-be-expanded portions 8. Upon application of the internal fluid pressure 99 acting in combination with the predetermined external volume of fluid 141, the fluids press the blank 100 flat against the screen 52 and platen 41 and concomitantly expands the portions 8 until they are flattened against the bottom of the die recess and until the external fluid 141 occupies all of the space remaining in the recess and is pressurized by the action of the internal fluid 99.

As illustrated in FIGURE 7 the sealing ring 46 is supported on and cooperates with the operative surface of platen 41 to define, with this surface, a holding pressure cavity for the external volume of fluid 141 employed for the desired one side expansion of blank 100. As can be seen, sealing ring 46 defines the side wall of the holding pressure cavity, and this ring is backed up by peripheral rim 45 to peripherally retain this sealing ring 46 against radial displacement during the one side inflation of blank 100.

The apparatus of FIGURE 8 illustrates that the recess may be placed in the upper as well as the lower platen, that the one-sided flattening pressure as well as the venting can be obtained by various procedures, and that the expansion may in some instances be less than the depth of the die recess.

The apparatus consists of a lower flat platen 151 and an upper recessed platen or die 150 having a peripheral rim 155 the contacting face of which is provided with an O-ring seal 154. Rim 155 and the O-ring 154 are adapted to press the blank for making article 171 in the vicinity of its periphery and close the recess of the die 150 thereabout. The recess of die 150 is associated with a water pressure applying tank 157 containing a main body of water 175 at any desired head. The volume of water 17 is admitted from the tank 157 to the die recess by means of the inlet opening 159 under the control of the valve 160 while venting of the die recess is obtained by means of the standpipe 163 and also by means of the evacuation pipe 161, both of which pipes are controlled by a gang valve 164.

In operation, the upper recessed die 150 and its associated tank 157 are moved into and out of engagement with the blank 171 by any suitable means such as the drive members 158.

With the valve 160 in closedposition, die member 150 is lowered upon a blank positioned on the platen 151 which contains a vacuum connection 178 communicating with the series of vents 177 leading to the flat face 152 of platen 151. With the valve 1160 opened, liquid is admitted to fill the die recess with the blank hold-down liquid 174 to act on the outside of the blank. Next, the internal inflation fluid 176 is injected into the unjoined interior areas of the blank, wherein it is maintained for a short time, as indicated below and in Table I, at the pressure necessary to develop the distentions 172 for article 171 to the shape desired and permitted by the confining fluid 174 at its pressure head. Under the combined pressures and with the aid of vents 177, the article is maintained in a high degree of flatness against the surface 152.

With the blank thus worked to the shape of the final finished article, valve 160 is closed. The internal fluid pressure 176 is then relieved. The valve 164 is opened to permit energizing of the pump 162 to empty the recess of the portion of water 174 therein. The upper die is then lifted from the finished sheet 171 and the vacuum relieved to complete a cycle of operation.

According to one example of the practice of this invention an inflatable blank of suitably knurled or embossed aluminum about 0.060 of an inch thick and having a tube wall thickness, each about 0.030 of an inch in the unjoined portion defined by a stratum of weld preventive, was expanded with a hydraulic pressure of about 2800 p.s.i. applied internally for a short time and concurrently with external confining hydraulic pressure applied by a pressure cylinder and limited to a maximum varying from about 1400 p.s.i. to 1300 p.s.i. with satisfactory results. This pressure of about 2800 p.s.i is the expansion pressure necessary to develop the desired distention in correlation with the specifically enumerated confining hydraulic pressure employed. As indicated above this expansion pressure of 2800 p.s.i. was applied internally for a short time in order to fully develop the desired distention, the value of which, as reflected in Table I, was found to be minimum of 3 seconds. Upon simultaneous release of both pressures, the amount of the distortion on the flat side was found to be negligible and never exceeded 0.005 of an inch at the higher external pressure. Even at the lower pressure the distortion was relatively negligible and was never more than about 0.010 of an inch at the few places where it was readily observable. Confinement between the faces of the die members imparted a desired flat contour to the top of the %-inch passageway distentions as well as to the flat side of the finished panel and served to gauge the expansion to an internal tube height of a nominal 0.060 of an inch.

In accordance with the practice of the invention at other pressure differential levels, many other surface embossed blanks of aluminum of about the same thickness were subjected at various operating conditions to obtain results as set forth in Table I which follows. with the indicated internal expanding water pressure the external reshaping and holding water pressure applied by pressure cylinder was varied as indicated in a press cavity such as to produce a total tube height of around 0.0120-0130 of an an inch. By varying the pressure differential, the departure from flatness on one side and the relative distention of both sides may be controlled to obtain desired configuration.

Table I Internal Pressure Applied Time* (Seconds) External Pressure, p.s.i.

Distortion UQMWCAIOOWUIUIOIOHPWM *Time indicates period of time the indicated Internal Pressure was applied internally of the inflatable blank concurrently with and during application of the indicated External Pressure on the face of the blank to urge and confine it against a die surface disposed adjacent the opposite face of the blank in accordance with this invention.

The hollow articles made in accordance with this invention may be expanded from various suitable blanks such as that disclosed in aforementioned US. Patent 2,690,002, for example, or that disclosed in co-pending patent application Serial No. 572,648 filed March 20, 1956 by Robert Milton Neel and Clarence A. Isbell, Jr.

The blank may be of any shape such as a flat or curved sheet, a cup, a cone, or other surface of revolution.

A particularly suitable blank is shown in FIGURE 9.

Such a blank is originally formed from two component sheets 180 and 181. Component 180 is thinner than component 181 the latter of which is preferably also different from the former by being harder because of a difference in composition and/or heat treatment. The unjoined areas 183 of the resultant blank are adapted for distention on one side over a portion of component 180 leaving the other side, surfaced by component 181 and having shallow elongated depressions 184, relatively flat. The surface depressions 184 act as pressure relieving vents for any air or liquid which may be trapped between the to-be-flat side of the blank and the flat platen of the inflation press especially in the absence of any pressure relieving depressions in the platen surface or absence of the relieving screen.

In the actual practice of the invention, however, maintenance of flatness has been found to present practical difficulties because of bending which occurs intermediate the beginning and end of the inflation and is localized at certain portions and particularly at the juncture of the unjoined end solid portions of the blank. While continued inflation of the blank tends at high pressure to erase such intermediate bending in certain instances and particularly where the blank has a cavity design with many sharp corners, the ultimate lack of perfect flatness is noticeable to an undesired degree, unless the blank is modified on one side to resist deformation. In accordance with a further aspect of this invention, it has been found that blanks of the type shown in FIGURES l and 11 result in a finished article having an undistended side of improved smoothness or substantial flatness.

The blank of FIGURE consists of a first component 280 and a second component 281 the latter of which is adapted to form the flat side of the finished article upon inflation of the unjoined portions 283 of the blank. The surface of the side of the blank formed by component 281 is provided with depressions 284 by any suitable plastic deformation method such as stippling, knurling or rolling of the blank at a reduction of about 10% or more simultaneously with a relatively undeformable mandrel member such as a hard sheet with protrusions or a metal screen. In the locale of each depression 284 the adjacent subsurface metal has been found to be work hardened as at 285. The effect of the worked areas 285 is to produce an overall surface stiffening in the blank.

The blank of FIGURE 11 consists of a relatively thin component side 38f) joined at portions 382 to a relatively thick component side 3581 while remaining unjoined at portions 383. Component 381 is not only thicker but also harder than component 380. The immediate subsurface layer 385 of component 381 is additionally and uniformly work hardened as compared to the rest of component 380 over the entire surface by shot peening at the surface 384. This is particularly advantageous where depressions or stippling are not desired on the flat side of the blank to interfere with a desired surface finish and where the partial surface hardening effect of stippling or knurling is not sufficient for certain applications. This section of the blank will be found upon inflation to final finished configuration to be quite flat on one side and to be well distended on the other side in the sections of component 380 underlying portions 383.

To produce the finished article from such blanks it is positioned between the open die members with the scored, pitted, knurled or peened side adjacent the rigid flat or smooth die member and then expanded. Afterward the pitted side may be polished if such surface deformations are objectionable in its further use.

Following expansion of the blank, the pressures may be released simultaneously, instantaneously or slowly in such desired ratios of pressures as are found suitable by the operator for each particular condition of composition, thickness, hardness, or final height of distention.

While. the foregoing has been described chiefly with reference to incompressible fluids such as suitable liquids as the preferred embodiment, it is to be understood that those skilled in the art may employ compressible fluids particularly as the internal inflation fluid and even as the hold-down fluid. One advantage of an incompressible liquid for external hold-down pressure application as compared to resilient or compressible members such as gases or pads is that upon relieving the internal pressure, the external pressure also may be spontaneously relieved. Furthermore, during application of the pressure, the externally applied liquid acts as if it were a solid cavitated die free from the resilience which tends to press back upon the work piece and impair the shape of the passageways developed by distention. Compressible fluids, unless carefully controlled, act like a premature internal pressure release and tend to collapse the distended portion of the article as evidenced by caving-in along the crests of the protrusions.

There is still another advantage in that a fluid in contrast to a resilient solid hold-down member will act upon the unexpanded area of the blank intermediate the distentions from beginning to end of the hold-down period whereas a solid applies itself later to such area and disengages from it prematurely with resultant impairment of the contour of the flat side.

Although the foregoing embodiments are now believed to be preferred, it is to be further understood that other changes and modifications may be made by those skilled in the art without departing from the spirit and scope of this invention and that the foregoing is intended by way of an illustration of the invention rather than as a limitation except as set forth in the appended claims.

What is claimed is:

1. An apparatus for expanding a hollow article from a blank provided with an expandable unjoined interior portion between first and second opposed faces thereof, comprising (A) first and second opposed platens having parallel operative surfaces in relatively movable relationship toward and away from each other and adapted to receive said blank therebetween;

(B) sealing means supported on the surface of said first platen circumscribing a portion of the surface thereof of an area encompassed within the periphery of said blank when said blank is placed on said sealing means in operative relationship therewith, said sealing means being adapted to confine a fluid under pressure between said first face of said blank and said first platen when said blank is disposed in operative relationship on said sealing means;

(C) means for moving said second platen toward said first platen to urge said blank into operative relationship with said sealing means;

(D) means associated with said second platen comprising means venting the space between the surface of said second platen and said second face of said blank for assuring intimate contact therebetween;

(E) means for applying a fluid at a first pressure level between said first face of said blank and said first platen within the circumscribed portion thereof; and

(F) means for applying a fluid pressure at a second level to said unjoined interior portion of said blank sufliciently in excess of said first pressure level to distend said blank.

2. An apparatus in accordance with claim 1 wherein said sealing means comprises a resilient gasket.

3. An apparatus in accordance with claim 2 further including confining means disposed on said first platen surrounding said gasket to limit movement of said gasket in a direction parallel to the surface of said first platen.

4. An apparatus in accordance with claim 3 wherein said confining means comprises a peripheral rim surrounding said gasket.

5. An apparatus in accordance with claim 4 wherein said rim has a thickness less than said gasket so as to be spaced from said blank when said blank is disposed in operative relationship on said gasket.

6. An apparatus in accordance with claim 1 further including means for concurrently releasing all said pressures.

7. An apparatus for expanding one side of a pressure welded passageway panel, comprising (A) a pair of relatively movable platens having opposed operative surfaces adapted to receive opposed faces of said panel therebetween,

(B) means associated with one of said platens comprising means for venting the space between the surface of said one of said platens and the face of said panel adjacent said surface of said one of said platens for assuring intimate contact therebetween during expansion of said panel, and

(C) means on the other of said platens forming a cavity for the desired expansion of said panel.

8. An apparatus according to claim 7 wherein said means for venting comprises a screen on said surface of 5 said one of said platens.

9. An apparatus according to claim 7 wherein said means for venting comprises a plurality of openings in said surface of said one of said platens.

References Cited by the Examiner UNITED STATES PATENTS CHARLES W. LANHAM, Primary Examiner. 

1. AN APPARATUS FOR EXPANDING A HOLLOW ARTICLE FROM A BLANK PROVIDED WITH AN EXPANDABLE UNJOINED INTERIOR PORTION BETWEEN FIRST AND SECOND OPPOSED FACES THEREOF, COMPRISING (A) FIRST AND SECOND OPPOSED PLATENS HAVING PARALLEL OPERATIVE SURFACES IN RELATIVELY MOVABLE RELATIONSHIP TOWARD AND AWAY FROM EACH OTHER AND ADAPTED TO RECEIVE SAID BLANK THEREBETWEEN; (B) SEALING MEANS SUPPORTED ON THE SURFACE OF SAID FIRST PLATEN CIRCUMSCRIBING A PORTION OF THE SURFACE THEREOF AN AREA ENCOMPASSED WITHIN THE PERIPHERY OF SAID BLANK WHEN SAID BLANK IS PLACED ON SAID SEALING MEANS IN OPERATIVE RELATIONSHIP THEREWITH, SAID SEALING MEANS BEING ADAPTED TO CONFINE A FLUID UNDER PRESSURE BETWEEN SAID FIRST FACE OF SAID BLANK AND SAID FIRST PLATEN WHEN SAID BLANK IS DISPOSED IN OPERATIVE RELATIONSHIP ON SAID SEALING MEANS: (C) MEANS FOR MOVING SAID SECOND PLATEN TOWARD SAID 